| Document and Entity Information | May 21, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | May 21, 2021 |
| Entity Registrant Name | CANADIAN PACIFIC RAILWAY LTD/CN |
| Entity Incorporation, State or Country Code | Z4 |
| Entity File Number | 001-01342 |
| Entity Tax Identification Number | 98-0355078 |
| Entity Address, Address Line One | 7550 Ogden Dale Road S.E. |
| Entity Address, City or Town | Calgary |
| Entity Address, State or Province | AB |
| Entity Address, Country | CA |
| Entity Address, Postal Zip Code | T2C 4X9 |
| City Area Code | 403 |
| Local Phone Number | 319-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000016875 |
| Amendment Flag | false |
| Common Shares, without par value, of Canadian Pacific Railway Limited [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Shares, without par value, of Canadian Pacific Railway Limited |
| Trading Symbol | CP |
| Security Exchange Name | NYSE |
| Perpetual 4% Consolidated Debenture Stock of Canadian Pacific Railway Company | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Perpetual 4% Consolidated Debenture Stock of Canadian Pacific Railway Company |
| Trading Symbol | CP40 |
| Security Exchange Name | NYSE |
